色散平坦渐减光纤中抽运残余成分的抑制与平坦超连续谱的产生(英文)

Suppression of Residual Pump Component for Flat Supercontinuum Generation in Dispersion-Flattened Dispersion-Decreasing Fibers

基于广义非线性薛定谔方程,通过数值模拟研究了色散平坦渐减光纤中抽运残余成分的抑制.研究结果表明:超连续谱的形状由输入孤子阶数N、归一化二次色散系数Δ2和归一化有效光纤长度ξ0决定.对于给定N和给定Δ2值的抽运脉冲,超连续谱的形状依赖于ξ0.通过合适地选取ξ0,抽运残余成分可以被有效地抑制并获光谱平坦度令人满意的超连续谱.为了获得参量ξ0的最优值,引入了S因子评价超连续谱的波动.S因子值越小,所产生的超连续谱越平坦.保持N和Δ2不变,计算了ξ0取不同值时,所产生的超连续谱的S因子.当S因子达到最小值时,抽运残余成分被抑制到最大限度,并获得最平坦的超连续谱,相应的ξ0值即为归一化参量ξ0的最优值.计算了N在1.0~2.2范围内,ξ0的最优值.结果显示当N降低时,ξ0的最优值增大.为产生具有弱残余抽运成分的超连续谱,抽运脉冲采用低阶孤子要优于高阶孤子.

Numerical simulations based on generalized nonlinear Schrdinger equation were used to study the suppression of residual pump component of supercontinuum generated in dispersion-flattened dispersion-decreasing fibers.The results show that the shape of a supercontinuum spectrum is uniquely specified by the input soliton order N,the normalized quadratic dispersion coefficientΔ2and the normalized effective fiber lengthξ0.For a pump pulse with a given Nand a given value ofΔ2,the shape of a supercontinuum spectrum depends onξ0.By appropriately choosingξ0,the residual pump component can be suppressed effectively and a supercontinuum with desirable spectral flatness can be obtained.In order to obtain the optimal value ofξ0,S-factor is introduced to estimate the fluctuation of supercontinuum spectrum.The smaller the value of S-factor,the flatter the generated spectrum.Keeping N andΔ2constant,S-factor of the generated supercontinuum spectrum for different value ofξ0was calculated.When S-factor reaches a minimum value,the residual pump component is suppressed to the utmost extent and a flattest supercontinuum spectrum is obtained.The correspondingξ0is the optimal value ofξ0.The optimal value ofξ0for the pump pulses with soliton order Nin the range 1.0≤N≤2.2was calculated.It isfound that when N decreases,the optimal value ofξ0increases.To generate a supercontinuum spectrum with weak residual pump component,lower-order soliton pulses are preferable to higher-order soliton pulses.